The present disclosure relates to semiconductor fabrication, and more specifically, to a centering fixture for an electrostatic chuck system and method of training an automated handling system.
In semiconductor wafer fabrication, each wafer is transported between a large variety of semiconductor processing systems to conduct different fabrication processes on a wafer. The tasks carried out by each chamber can vary, e.g., deposition, etching, etc. Wafers are moved by automated handlers within and between processing systems. The automated handlers pick up the wafers from one processing system, and move them to a next processing system or within a processing system.
Certain processing systems include a task specific chamber that includes an electrostatic chuck (ESC) system to hold the wafer in a desired location. An ESC system may include a chuck or platen that can be electrostatically charged to hold a wafer in position on the chuck. The chuck may be circular or another shape. In addition, an ESC system includes a set of retractable lift pins upon which a wafer is positioned by an automated handler in a centered fashion relative to the chuck. A wafer that is centered on a respective ESC system in a processing chamber is in an ideal position for accurate and repeatable processing by the particular processing system.
Automated handlers include a carrier arm that carries the wafer and positions it on the set of retractable lift pins in a centered fashion relative to the chuck during entry of the wafer to the respective processing system. Retraction of the lift pins positions the wafer in a centered position on the chuck. Regardless of the processing system, it is important that the wafer is located within the processing system relative to its respective ESC system in a precise and repeatable centered manner so that the subsequent processing can be performed in a repeatable fashion, e.g., uniformly etching the wafer. In order to achieve this precision and repeatability, each automated handling system and, in particular, an aligner system thereof, is calibrated to position the carrier arm of the automated handler such that the wafer is centered relative to the chuck. That is, the aligner system is taught to know the centered location for a wafer relative to the chuck for future reference and use in placing wafers to be processed by the particular system.
One challenge relative to automated handling system calibration is centering the wafer within a particular processing system relative to the chuck. Conventionally, during calibration, a wafer is placed on the chuck within a selected processing system and is visually centered by a user. The aligner system is then calibrated (taught) based on the visual centering. Human variation can adversely impact the calibration.